The invention relates to a closure cap that maybe brought into engagement with a container.
Closure caps of plastic material are used in a multitude of applications for closing containers. For achieving an adequate sealing effect, it is known to lay a sealing inlay of a softer material onto the inner side of the cap base. So that the outer upper edge of the container to be closed is adequately sealed, it is for example known in EP 55 916, in the region of the transition between the cap base and the cap skirt, to provide a circumferential pressing bulge which presses the sealing disk against the edge of the container opening. With such a design, good sealing results are achieved.
If such closures are used in combination with a container in which in the course of time an increased inner pressure may build up, the good sealing property may lead to certain problems. If the inner pressure in the container, for example, increases by heating or by fermentation of the contents, on account of the good sealing there exists the risk that the container explodes.
EP 370 272 therefore suggests providing the circumferential bulge with segment-like interruptions. In the region of these interruptions the sealing inlay may be pressed outwards. With this gas may escape and the inner pressure may be reduced.
The closure cap according to EP 370 272 is however burdened with the disadvantage that in the region of the segment-like interruptions the sealing effect also with a normal inner pressure is no longer optimal. With this there exists the danger of leakages under normal conditions.
It is a goal to provide a closure cap which permits an adequate sealing of the container opening at normal conditions and which in spite of this permits the reduction of an increased inner pressure.
The closure cap for a container comprises a cap base and a cap skirt. The cap skirt is provided with inner retaining elements which can be brought into engagement with outer retaining elements on the opening of the container. The closure cap furthermore comprises a sealing disk which at least partly lies on the cap base and which can be pressed against the opening of the container. The closure cap is furthermore provided with a bulge in the transition region between the cap base and the cap skirt. The bulge serves for pressing the sealing disk onto the upper, outer edge of the opening of the container. The bulge is furthermore divided by at least one segment-like interruption into several blocks. If the inner pressure in the container rises, the sealing disk in the region of the interruptions may be forced radially outwards, by which means a reduction of the inner pressure is made possible. Of course the sealing disk may also be formed annularly.
The closure cap is, because of the venting behavior, above all particularly suitable for carbonated beverages, fruit juices and hot fillings.
According to the present invention the cap base on its inner side is provided with at least one rib running radially outwards. The rib extends radially at least over one sealing section on the inner side of the head plate. Sealing section here and in the following is to be understood as a section of the inner side of the head plate by way of which the sealing disk can be pressed against the opening of the container to be closed, in particular against the end-face side. The rib on the inner side of the cap base, seen in the circumferential direction, is arranged neighbouring the interruptions between the individual blocks of the bulge for the pressing of the sealing disk.
The arrangement of the radial ribs neighbouring the interruptions leads to a reliable sealing and in spite of this ensures venting of gas at an increased inner pressure. With a normal pressure the sealing disk in the region of the radial rib is pressed against the container opening. Also in the region of the interruption between the blocks of the bulge therefore a good sealing is ensured. If however the inner pressure in the container rises the cap base on account of the increased inner pressure is raised (so-called doming). With this the radial ribs are relieved of pressure. The sealing effect of the sealing disk in the region of the interruptions between the blocks of the bulge is as a result reduced. The excess pressure may therefore vent particularly well in the region of the rib and the interruption.
Preferably several interruptions are arranged in the bulge so that there are formed several blocks. Advantageously at least one radial rib is arranged radially flush to each interruption. This leads to a particularly uniform venting function. It is however also conceivable to arrange several radial ribs for each interruption. With several ribs, additionally between the ribs there is formed a venting channel into which the sealing disk may be displaced.
Preferably the angular extension of the ribs is selected smaller than the angular extension of the interruptions. As a result between the outer bordering line of the rib and the interruption between the blocks, additionally channels for venting are formed. With an increased inner pressure the sealing disk may be displaced into these channels.
Preferably the closure cap is roughly provided with 9 interruptions and 9 blocks and radial ribs. This value corresponds to an optimal compromise between sealing and bleeding properties.
The interruptions advantageously extend over an angle of about 5xc2x0 to 30xc2x0.
For increasing the pressing of the sealing disk additionally on the cap base there is provided a circumferential rib which has a lesser thickness than the radial rib.
The invention is hereinafter described in more detail in embodiment examples and by way of the drawings.